Cognitive Neuroscience Lecture 16: Attention 2
L16: Attention 2 What are the units of attention? - Features: Feature-based attention o Attention to a visual feature (e.g. color, orientation, texture) resulting in enhanced representation of image components related to this feature throughout visual field o Pop-out: '''green scarves among red § '''Single deviant features are detected quickly o Hard feature search: bald man at a rock concert is hard o Conjunction search: where’s waldo requires conjunction of several features: spatial frequency (shirt stripes), colors, orientation o Visual search response time: § Pop out search takes same amount of time regardless of sample size § Conjunction search takes more and more time as set size increases o Attention capture § Report the GREEN letter § Presented with a green ‘#’ § Distractor in the same ‘Attentional set’ (green) captures attention: contingent capture ''' o Attend to motion vs. attend to color § Subjects pay attention to either motion or color depending on instructions § Same stim every trial, but only attend to some § '''Attending to motion modulates medial temporal regions/V5 · Lateral occipitotemporal regions § Attending to color modulates ventral area V4 (posterior fusiform gyrus) § Same result from fMRI and MEG § Attention modulates activity in feature-specific visual cortex ''' o Effects of feature-based attention § '''Attention modulates brain areas involved with processing attended features · Inflating and flattening a brain: sulci and gyri mapped onto continuous, smooth surface. · NOTES - Objects & Categories o Object-based attention: 'can attention be allocated to objects? § Cuing spatial attention to a location in space can improve target detection § What about spatial attention ''within ''objects? § Object-based orienting § RT shortest for cued valid, longer for invalid same obj, and longest for invalid diff obj ß controlled for distance from cue and target § %signal change difference (i.e. same-object activation) increases as you look at progressively higher visual areas § Attention is a higher-level process o '''Object-based attention deficit: object-based neglect ' § Loss of attention/awareness to left side of ‘object’, not necessarily space § Spatial neglect: IPL, TPJàexogenous § Object based neglect: even more ventral regions (STG) § '''Balint’s Syndrome · Object-based attention deficit · Following damage to both '''parietal lobes · Can only see 1 object at a time (simultaneous agnosia) · ‘Attentional tunnel vision’ · Typically temporary · Normal visual acuity, depth perception, motion perception, object recognition, etc · Balint’s syndrome patient wouldn’t be able to tell if 2 lines were same length or not (since he can only see 1 line at once) o However, he would know it’s a trapezoid bc all lines connected à one obj · Star of David is a star if all same color; if 2 diff colors, it’s 2 triangles · '''Local vs Global: NOTES o Category-based attention § What we attend to in real life is often more complex than simple features, e.g. people, buildings, cars, etc. § Category-based effects · When told to attend to motion and… o …Face movesàFFA more active o …Place movesàPPA more active · Category-based attention enhances response of corresponding category-selective visual regions · · Fs>F because attention modulates category selective visual regions (same for Sf and S) § Some targets of attentional modulation in vision (areas whose activity is modulated by attention): Ventralish · STG: early audition · hMT+motion · V1—V4: early vision · Fusiform gyrus & parahippocampal gyrus: faces/houses § Some sources '''of attentional control: Dorsalish § § Supports dual network theory - '''Time: temporal attention o Time perception—time’s subjective expansion § Does attention to an object increase its perceived duration, i.e. expand time? o Oddball expansion: different types of oddball events tested § Time expansion for oddballs o Attentional blink: what are the two digits? § See first but not 2nd because of lag § Stage 1: ALL STIM · Stim activate conceptual representation (number/letter) · Fast, capacity unlimited · Conceptual representations fleeting & overwritten rapidly § Stage 2: TARGET STIM: bottleneck · When target detected, must be protected so that it isn’t overwritten · Triggers encoding/consolidation in working memory · Slow, severely capacity limited · Other representations have to wait (and risk being overwritten) o You don’t remember the 2nd digit because stage 1 isn’t as effective when you’re busy with stage 2 o Evidence for 2 stages: 'dissociation in brain ' § Correct identification of T2, missing T2, or Correct rejection § Stage 2: frontal regions respond only to detected (hit) T2 § Stage 1: ventral temporal regions respond to detected and undetected T2 § o Change blindness: § More likely to notice if they change groups § Change depends on what you ‘attend’ to § Same social group effect § 'If you only encode type/category, you will fail to recognize an exemplar change '